A jaw crusher is a device suitable for crushing stone. FIG. 1 shows a known jaw crusher 100 at maximum setting and FIG. 2 shows the jaw crusher of FIG. 1 at minimum setting. A jaw crusher comprises two crushing elements i.e. jaws 10 that are arranged to receive the forces generated during operation of the crusher or for example while changing the setting of the crushing elements. One crushing element is a substantially immobile fixed jaw supported on a frame 4, and the other crushing element is a jaw attached to a pendulum and configured to be movable. The crusher further comprises a pendulum 11 attached through a bearing from the top end thereof to an eccentric 12 causing the top end of the pendulum 11 to rotate around the centre axis of the eccentric. A toggle plate 1 functioning as a linkage for the pendulum is situated between the bottom end of the pendulum and the back end of the jaw crusher. The toggle plate and the linkage provide for the desired kinematics of the crusher in order to achieve effective crushing. The toggle plate is attached at one end with separate connecting elements to the pendulum and at the other end to the piston rod of a hydraulic cylinder 9 functioning as a safety apparatus in such a way that the piston rod is in connection with the crushing element configured to be movable. Both ends of the toggle plate 1 comprise connection elements 3 that comprise toggle plate bearings between the pitman 1 and the connecting elements 3. The upper connecting element is fitted between the guide elements 6 in such a way that during the crusher setting adjustment or during an overload situation, the connecting element can glide along the guide elements towards the hydraulic cylinder while the piston is pressed further into the cylinder. The piston of the hydraulic cylinder of the safety apparatus supports the movable jaw from the outer side.
If the force or strain incident on the movable jaw is too large, the toggle plate may give in, i.e. a so called buckling takes place, and thus protect the crusher from further damage. In addition to the toggle plate, the hydraulic cylinder and a safety valve form a further safety apparatus, since the space 16 behind the piston has a connection through the safety valve to a hydraulic fluid tank.
The crusher according to FIGS. 1 and 2 further comprises a return cylinder 2 which is a double acting cylinder. The return cylinder is attached to the crusher frame for example at a bracket next to the cylinder 9 of the safety apparatus. The return cylinder is connected to a hydraulic accumulator 15 that holds the piston rod side of the return cylinder pressurized during operation in order to ensure tension. The return cylinder 2 is also utilized in enlarging the setting, since the cylinder of the safety apparatus is single acting.
FIG. 3 shows a system 300 that demonstrates the functioning of the hydraulic cylinder 9 of the safety apparatus. The hydraulic cylinder 9 has a piston 316 dividing the volume of the cylinder into a pressure space 312 and opposite space 314, i.e. the piston rod side space. The piston rod 318 receives the load or force incident on the piston from the toggle plate. The load causes a pressure equivalent to the amount of force divided by the cross-sectional area of the cylinder into the pressure space. As the pressure exceeds a given pressure threshold, a pressure relief valve PRV 360 connected to the pressure space 312 allows hydraulic fluid from the pressure space to a hydraulic fluid tank 320 whereupon the toggle plate and the movable jaw are allowed to give before the excessive load. This is beneficial for example if uncrushable material such as steel or the like ends up between the jaws. The piston 316 is driven back to its desired position by pumping hydraulic fluid into the pressure space 312 with a pump 330. A valve 340 is used to control the filling of the pressure space 312 in such a way as to steer the piston to its desired position.
The crushing elements, the pendulum and the cylinder of the safety apparatus of the jaw crusher receive large crushing forces during crushing and move several times per second. The required wear resistance is taken into account in the structure of the jaw crusher by using sufficiently large material strengths and wear resistant surfaces in such a way that on one hand a sufficient durability is reached and on the other hand creating costs is avoided. In addition, the crushing capacity of the jaw crusher that is dependent on the efficiency of the crushing impacts is sought to be maximized and the energy consumption of the crusher is sought to be minimized.
Patent publication FI20095429 (A) shows an arrangement with which undesired give of a cylinder can be reduced in order to increase the efficiency of a crusher.
The purpose of the invention is to avoid or lessen problems related to the state of the art and/or provide new technical alternatives.